Ulnar shortening osteotomy for ulnar impaction syndrome

Indications

Indications for the procedure include:

• Inherited or acquired ulnocarpal abutment (ulnar impaction syndrome)

• Posttraumatic incongruency of the distal radioulnar joint (DRUJ)

• Loss of radial height associated with distal radius fracture malunion

• Madelung deformity or premature physeal closure of the distal radius

Clinical examination

• Patients present with ulnar-sided wrist pain with swelling and decreased range of motion of the wrist. Ulnar-sided wrist pain is a symptom of various conditions, and these must be investigated with physical examination and radiographic or arthroscopic techniques.

• Other common causes of ulnar-sided wrist pain include triangular fibrocartilage complex (TFCC) injuries, DRUJ instability or arthritis, extensor carpi ulnaris (ECU)/flexor carpi ulnaris (FCU) tendinopathy, carpal fracture or instability, vascular (hypothenar hammer syndrome), or neurogenic pathology (ulnar dorsal sensory neuritis, compression in the Guyon canal).

• The ulnocarpal stress test and ulnar foveal signs may be positive with ulnocarpal abutment, but neither is specific.

• The ulnocarpal stress test (TFCC grind test) attempts to recreate ulnar-sided wrist pain when the wrist is maximally ulnarly deviated and axial-loaded. The maneuver is tested while the wrist is passively put through the arc of pronation and supination. A positive ulnocarpal stress test may be caused by ulnocarpal abutment or isolated TFCC injury. Extreme pronation brings the carpus in line with the ulnar head and will likely exacerbate pain with ulnar loading if ulnar abutment is present ( Fig. 29.2 ).

  

• The ulnar foveal sign is a provocative maneuver that is useful in diagnosing foveal detachment of the TFCC or ulnotriquetral ligamentous injury. The examiner identifies the interval along the ulnar side of the wrist between the pisiform and the ulnar styloid and applies direct pressure with the wrist and forearm in neutral position ( Fig. 29.3 ).

  

• To perform a pisiform boost, while simultaneously depressing the ulnar head with volar-directed force and applying dorsally directed pressure on the volar aspect of the pisiform, the patient is asked to both actively and passively ulnarly deviate the wrist. This provocative maneuver loads the central portions of the ulnar dome, TFCC disk, lunate, and triquetrum. A painful positive test suggests TFCC pathology, ulnar abutment, or DRUJ arthritis.

Imaging

• Standard posteroanterior (PA), oblique, and lateral x-rays of the wrist are obtained with a particular interest in the relationship between the articular surfaces of the distal ulna and the radius. Ulnar variance is measured on a neutral rotation PA view with the shoulder and elbow at 90 degrees. When the lunate facet of the distal radius and dome of the ulna are measured at the same level, this is termed neutral variance and is seen in 12% of the general population ( Fig. 29.4 ). If the ulnar articular surface is distal to the lunate facet of the radius, this is called positive variance (55%). Negative ulnar variance exists when the ulna is proximal to the radius (33%). Normal variance is considered to be −2 mm to +2 mm. Pronation (up to +1 mm) and power grip (up to +2.5 mm) may change the articular relationship ( Fig. 29.5 ). Considering the wide range of so-called “normal” variance, always check a contralateral x-ray before deciding on the diagnosis/treatment for ulnar abutment.

  
  

• Ulnar-positive variance may be associated with ulnocarpal abutment. Other radiographically apparent features of this disorder include cystic changes or sclerosis of the ulnar corner of the lunate, the triquetrum, or the radial portion of the ulnar head ( Fig. 29.6 ).

  

• Magnetic resonance imaging (MRI) may be useful in identifying changes associated with ulnocarpal abutment. Short T1-weighted inversion recovery images and fat-suppressed T2-weighted images may reveal subchondral bone marrow edema and early chondromalacia ( Fig. 29.7 ). Focal proximoulnar cystic changes in the lunate (see Fig. 29.7 ) are a pathognomonic radiographic finding of ulnar abutment.

  

• Wrist arthroscopy can be used to accurately diagnose ulnocarpal abutment and to rule out other associated pathology of the wrist. A large central TFCC perforation with associated articular wear of the ulnar head or proximal articular cartilage of the lunate or triquetrum suggests that the bones are contacting.

• The distal radioulnar joint must be examined radiographically for signs of arthritis because this could contribute to wrist pain and may be exacerbated by shortening the ulna.

Surgical anatomy

The ulnocarpal joint transmits around 20% of the load across the neutral ulnar wrist, whereas the radiocarpal joint transmits around 80% of the load. Load transmission across the ulna in patients with 2.5-mm positive ulnar variance increases to 42%. This considerable increase in load with ulnar-positive variance puts the wrist at a high risk for articular degeneration and ligamentous injury. Increased dorsal tilt of the radius can further exacerbate loading onto the ulnar side of the wrist. With 2.5-mm negative ulnar variance, the load transmission decreases to 4.3%. This is the basis for the ulnar shortening osteotomy.